An image forming apparatus, such as a copying machine, forms an electrostatic latent image of an intended image by selectively exposing numerous points on the peripheral surface of a photosensitive drum according to image formation data. Then, the electrostatic latent image is developed with developer into the intended image. Thereafter, the developed image is transferred onto a recording medium.
Thus, an image forming apparatus, such as a copying machine, has to be supplied with developer each time it runs out of developer.
As for the means for supplying an image forming apparatus with developer, it is a common practice to employ a single or plurality of various developer supply containers, which may be roughly grouped into two types: the so-called dumping type that delivers all at once the entirety of the developer therein into the developer receiving container of the main assembly of an image forming apparatus, and the so-called trickling type (or installation type) that is left in the main assembly of an image forming apparatus to gradually deliver the developer therein into the developer receiving portion of the main assembly.
The trickling type developer supply container is structured so that it discharges developer by receiving a rotational driving force from the motor with which an image forming apparatus is provided.
For example, the developer supply container disclosed in Japanese Laid-open Patent Application 2002-072649 is of the so-called bag-in-box type, which is made up of an external box as a protective casing, and a flexible bag as a toner bag placed in the external box. This developer supply container is also provided with a powder pump, to which driving force is given from the main assembly side of the image forming apparatus to convey the developer in the container.
However, a developer supply container, such as the above-described one, in accordance with the prior art is structured so that the mechanism for conveying developer receives the force for driving the mechanism, from the main assembly side of an image forming apparatus. In other words, an image forming apparatus must be provided with the drive train for transmitting the driving force to the mechanism for conveying developer.
Providing an image forming apparatus with a driving mechanism, such as a drive train complicates the image forming apparatus in structure, possibly increasing the image forming apparatus cost and energy consumption.
Further, according to the prior art, the mechanical power source for driving the developing device(s) of an image forming apparatus is also used to drive a developer supply container, limiting thereby the area in which the developer supply container is installable, to the areas which are immediately next to the system for driving the developing device(s); in other words, where a developer supply container is installable in an image forming apparatus is limited. The adjacencies of the developing device(s) are occupied by a photosensitive drum, an exposing apparatus, a cleaner, etc., affording therefore little space for an additional component. This has been one of the essential impediments in increasing a developer supply container in developer capacity or reducing in size the main assembly of an image forming apparatus.